Field of the Invention
The invention relates to an improved process for preparing halogenated biphenylanilides and biphenylanilines by Suzuki coupling of bromo- or iodoanilides or bromo- or iodoanilines with chlorinated organoboron compounds. Biphenylanilides and biphenylanilines serve as precursors for preparation of crop protection agents having fungicidal action.
Description of Related Art
Palladium-catalysed cross-coupling of halogenated aromatics of the formula (II) with organoboron compounds of the formula (III), according to WO 2006/092429, WO 2007/138089 and WO 2009/135598, affords both halogenated biphenylanilines and halogenated biphenylanilides of the general formula (I) according to Scheme 1 below.
where the substituents are each defined as follows:    X is hydrogen, fluorine or chlorine;    Hal is halogen    R1 is selected from a protected amino group, NO2, NH2 and NHR3;    R2 is selected from cyano, nitro, halogen, C1-C6-alkyl, C1-C6-alkenyl, C1-C6-alkynyl, C1-C6-alkoxy, C1-C6-haloalkyl, (C1-C6-alkyl)carbonyl and phenyl;    R3 is selected from hydrogen, —CH2-(C═O)CH3, C1-C8-alkyl, C1-C8-alkenyl, C1-C8-alkynyl and C6- C18-aryl    n is selected from 1, 2 and 3,    p is selected from 1, 2, 3 and 4 and    Q is selected from hydroxyl, F, Cl, Br, I, C1-4-alkyl, C6-10-aryl, C1-4-alkoxy and C6-10-aryloxy, C1-4-alkoxy radicals which, together with the boron atom to which they are bonded, form a 5- or 6-membered ring which may be substituted by C1-4-alkyl radicals
and the compounds of the formula (III) comprise different organoboron compounds.
The ligands used for the Suzuki reaction shown in the above scheme include unsubstituted and substituted trialkyl- or triarylphosphines. In addition, according to WO 2001/042197, dialkylarylphosphines are also suitable as ligands. The selection of possible phosphine ligands is extended by WO 2004/052939, p. 34 ff., to include phosphines in which one of the radicals on the phosphorus consists of a biphenylic base skeleton.
If, in the general formula (II), the substituent    Hal is bromine or iodine, and    X is hydrogen, fluorine or chlorine,
and the substituent R2 in the general formula (III) is chlorine,
chlorinated biphenylanilide or biphenylaniline formed under the conditions of the Suzuki reaction reacts further with boron compounds of the general formula (III) to give triaryls of the general formula (IV) and higher homologues thereof (Scheme 2). This results in a yield loss of the desired biphenylanilide or biphenylaniline of the general formula (I).Scheme 2

The extent to which this further reaction takes place is essentially determined by the phosphine ligand used in the reaction.
WO 2004/052939 describes the use of biphenylic phosphines and di(tert-butyl)phenylphosphine, which catalyse the Suzuki reaction of the aryl chlorides, which are less reactive compared to aryl bromides, with phenylboronic acids even under very mild conditions. It can be assumed in such a case that triaryls are formed to a noticeable extent.
Through the introduction of a protecting group on the nitrogen atom, it is possible according to WO 2009/135598 to reduce the proportion of triaryls. In the Suzuki reaction, it is possible to use either trialkyl- or triarylphosphines.